"He has to eat through a straw on a syringe. It's horrible," Shankman told PEOPLE at the GO GO Gala in Los Angeles on Thursday. "He's in great spirits. He's just like, 'Wow. It hurts.' His jaw is wired shut."

Shankman has also given Efron some good-natured tough love. "He's like my little brother, has been since Hairspray," Shankman said. "'So I talk to him like a little brother, which means I give him a lot of s––."

"He has always been a klutz," the director added. "And this is like a perfect Zac move."